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Trailer Wiring Diagrams
Eastern Pennsylvania
3871 Posts
November 15, 2010 - 9:56 am

4-Way Connectors
4-Way connectors are available allowing the basic hookup of the three lighting functions (running, turn, and brake lights) plus one pin is provided for a ground wire. Most standard light duty trailers will use a 4-pole flat connector.

5-Way Connectors
5-Way connectors are available allowing the basic hookup of the three lighting functions (running, turn, and brake) and besides the ground, one pin is available to provide support for another function. Typically the 5-Way Flat is used for trailers with surge brakes or hydraulic brakes. The additional wire is tapped into the backup lights to disengage the hydraulic trailer coupler (actuator) when the vehicle is reversing, thus turning off the trailer's brakes.

6-Way Connectors
6-Way connectors are available allowing the basic hookup of the three lighting functions (running, turn, and brake) the ground and two extra pins are available to provide two additional functions, typically for electric brakes and 12 volt "hot" lead. The 6-way round connectors are very common on horse trailers. The 6-way square connectors are more common on campers.

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7-Way Connectors
Aside from the three main lighting functions, additional pins for electric brakes, a 12 volt "hot" lead, and backup lights are available. There are two types of 7-way connectors. One has flat pins, which is often referred to as blades. The other has round pins. The round pin style is very rare. The RV style 7-way with flat pins (or blades) is very common. It is often found on newer trucks and suvs that come equipped from the factory with a trailer hitch.

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Mounting Your Trailer Wiring Harness
Often the 4-pole trailer connector will remain in the trunk or cargo area of a car or SUV when not in use. This helps to extend the life of the connector by protecting it from the elements and accidental damage. When it is needed for towing, simply pull the connector out and shut the trunk or rear door. The rubber weather strip that provides a door seal keeps the wire from getting pinched. If the trailer connector needs to be mounted under the vehicle, we offer many different mounting brackets that will help to protect the connector and keep it from dangling beneath the vehicle.

Trailer Wiring AdaptersThe T-One connectors and hardwire kits all use a 4-pole trailer connector. This connector is most common among the smaller utility trailers and can easily be adapted to match the larger 5-pole, 6-pole and 7-pole styles. Using an adapter lets you avoid having to splice into the vehicle's wiring system. Adapters will plug into the flat 4-pole connector and have wire leads to provide additional functions such as powering trailer brakes, power lead for utility lights, reverse, or auxiliary power for a winch or tools. If your vehicle or trailer is equipped with something other than a 4-way plug, such as the larger 7-way round plug, you can use our adapter fitguide to find the one that is right for your vehicle and trailer.

Some information has been provided by

Eastern Pennsylvania
3871 Posts
February 22, 2011 - 10:49 pm
Pin Connector Function Wire Color Suggested Minimum Wire Gauge Where To Attach - Vehicle Side Where To Attach - Trailer Side
      4 Way & 5 Way 6 Way & 7 Way    
7 Way 6 Way 5 Way 4 Way Right Turn Green 18 16 Right turn of vehicles wiring harness Trailers right turn signal
Left Turn Yellow 18 16 Left turn of vehicles wiring harness Trailers left turn signal
Ground White 16 12 Vehicle ground point - metal, uncoated, rustproof Vehicle ground point - metal, uncoated, rustproof
Tail / Marker Brown 18 16 Taillight of vehicles wiring harness Trailers taillights
  Brake Blue 18 12 Electric brake control, power for brakes Break away switch
    Battery Red (or Black)   12 Fuse block or FUSED battery Lead Break away kit, interior lights and battery charger.
      Backup Purple   16 Back up of vehicles wiring harness Back up lights (if available) / Hydraulic coupler.
108 Posts
April 9, 2012 - 8:16 am

the only problem I see with this post is that many PUP's/campers's use the odd (Bargman) Green is tail, red left, brown right. This is were many people get into trouble.

52 Posts
April 5, 2013 - 8:29 am

If I remember right , 6 pin Jaycos are wired a little differently. Please correct me if I'm wrong. I just remember a yr. or 2 ago going through tail light issues and hitting the good old internet to find the Jayco wiring diagrams. Getting old here , sorry !!!

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